Configure Metricbeat according to the example configuration below. Enter your modules and be sure to use the token from step 3 and add the message field. In our example we're using logstash for the output:

Alooma looks for a "message" field and treats it as the event. Any other fields are treated as the metadata. If the "message" field is missing, the events are discarded as invalid events. For Metricbeat, all the metrics information will be under the _metadata parent field in Alooma.